Chemistry Unit 2

History of atoms, ions and isotopes, light, light equations atomic spectra, electron configuration

Democritus

Democritus

First atomic model; discovered atoms.

John Dalton

Created atomic theory; model similar to Democritus’s.

Dalton’s Atomic Theory

• All atoms of the same element are identical and have the same mass.

• Atoms of different elements vary in size, mass, and chemical behavior.

• Chemical compounds are made up of at least 2 atoms of different elements. The resulting particle is called a molecule.

• In a chemical reaction, atoms are rearranged, separated, or recombined to form new compounds but no atom is created or destroyed.

JJ Thompson

Discovered the electron using the cathode ray tube experiment; proposed the chocolate chip model.

Ernest Rutherford

Discovered the nucleus and that the atom is mostly empty space using the gold foil experiment; created the nuclear model.

Niels Bohr

Discovered that electrons move in definite orbits around the nucleus; created the planetary model.

Erwin Schrodinger

Discovered that electrons move in clouds, not in definite orbits; created the quantum model.

Where is the atomic number?

above the element on the periodic table

Where is the atomic mass?

below the element on the periodic table

How do you find protons using the periodic table?

It is equal to the atomic number

How do you find electrons on the periodic table

same as protons

How to find neutrons using the periodic table

Subtract atomic number from atomic weight

Example: For Carbon (C), Z = 6, A ≈ 12, so Neutrons = 12 - 6 = 6.

Cation vs anion

Cation vs Anion

• Cation: A positively charged ion, formed when an atom loses one or more electrons. Example: Na⁺ (sodium ion).

• Anion: A negatively charged ion, formed when an atom gains one or more electrons. Example: Cl⁻ (chloride ion).

Cations and anions are essential in forming ionic compounds and play crucial roles in chemical reactions.

What is an isotope?

An atom with different amounts of neutrons than normal.

What is the top number in nuclear notation

the mass aka protons + neutrons. on the bottom is the atomic number aka number of protons only

Electromagnetic spectrum - lowest to highest

Radio, Microwave, Infrared, Visible (ROYGBIV), Ultraviolet, X-ray, Gamma ray.

photoelectric effect

when light above a certain frequency hits a metal, electrons are released. 2 ways to increase electrons emitted are to increase the frequency or to increase intensity

how is light created

photons goes into atom and excites it, goes back to ground state but it has to emit the photon/light. an atom will emit what it absorbs

atomic spectra

the unique range of wavelengths emitted by an atom/element. unique for every element so it helps identify elements

what is h in light equations

planck’s constant

what is the upside down y in light equations

wavelength usually in meters

what is c in light equations

speed of light

what is nu or v in light equations

frequency